The three-dimensional internal flow field of cross flow fans with 30°twisted blade was simulated with computational fluid dynamic (CFD) method. The influence of each structure parameters (volute case gap, volute throat gap, internal circumferential angle of the blade, external circumferential angle of the blade, blade numbers, the ratio of internal diameter to external diameter of the impeller or twisted angle of the blade) on the volume flow rate of the cross flow fan outlet was numerically researched. The optimal combination of seven structural parameters with the optimal performance of the cross flow fans was obtained by the orthogonal design method. Under the constant impeller external diameter and rotating speed, the optimal combination of structural parameters are as follows: volute case gap εc is 1mm, the volute throat gap εt is 2mm, the internal circumferential angle of the blade α is 90°, the external circumferential angle of the blade β is 20°, the blade numbers n is 30, the ratio of internal diameter to external diameter of the impeller γis 0.75, and the twisted angle of the blade θis 90°. It is obtained that the volume flow rate of the outlet of the optimized cross flow fan was increased by 25.2%. By means of the detection device of cross flow fan’s performance parameters, the air outlet average velocities of the optimized and original cross flow fans were experimentally tested under the constant impeller external diameter and different impeller rotating speeds. The experimental result showed the air outlet average velocities of the optimized cross flow fan were increased by 4.6%. The theoretical calculation results were consistent with the experimental test results. 